1. Field of tile Invention
The present invention relates to an apparatus for estimating defects or particles of an object to be inspected such as a semiconductor wafer and, more particularly, to a defect estimating apparatus capable of performing observation of internal defects or particles of an object to be inspected by distinguishing them from particles or flaws on the surface of the object.
2. Prior Art
As an apparatus for estimating defects or the like of an object to be inspected such as a semiconductor wafer, there is a conventionally known apparatus in which laser light is obliquely incident on the surface of an object to be inspected, and the resulting scattered light from internal defects is observed through the surface of the object in a direction different from the incident direction of the laser light, thereby detecting internal defects or particles of the object (Japanese Patent Laid-Open No. 4-24541). In this apparatus, the influence of reflected light is minimized by observing the scattered light from an object to be inspected in the direction different from the incident direction of the laser light. In addition, by changing the wavelength of the laser light or the temperature of an object to be inspected, the depth to which the laser light enters the object can be adjusted.
In this conventional technique, however, in observing internal defects near the surface of an object to be inspected, flaws or the like present on the surface are also observed in the same field of observation. In addition, internal defects of an object to be inspected cannot be distinguished from flaws or the like on the surface of the object. This makes an accurate estimate Impossible.